An exhaust gas sensor having an anticipatory controller may be positioned in an exhaust system of a vehicle to detect an air-fuel ratio of exhaust gas exhausted from an internal combustion engine of the vehicle. The exhaust gas sensor readings may be used to control operation of the internal combustion engine to propel the vehicle.
Degradation of an exhaust gas sensor may cause engine control degradation that may result in increased emissions and/or reduced vehicle drivability. Accordingly, accurate determination of exhaust gas sensor degradation and subsequent adjustments to parameters of the anticipatory controller may reduce the likelihood of engine control based on readings from a degraded exhaust gas sensor. In particular, an exhaust gas sensor may exhibit six discrete types of degradation behavior. The degradation behavior types may be grouped into filter type degradation behaviors and delays type degradation behaviors. An exhaust gas sensor exhibiting filter type degradation behavior may have a degraded time constant of the sensor reading while an exhaust gas sensor exhibiting delay type degradation behavior may have a degraded time delay of the sensor reading. In response to sensor degradation, anticipatory controller parameters may be adjusted to increase accuracy of the readings of the degraded exhaust gas sensor.
Previous approaches to adjusting parameters of the anticipatory controller of an exhaust gas sensor, responsive to degraded behavior, include reducing anticipatory controller gains irrespective of the type and magnitude of sensor degradation. In one example, to maintain stability of the anticipatory controller system, controller gains may be reduced aggressively to reduce system instability. However, adjusting controller parameters in this way may result in reduced performance of the air fuel control system.
The inventors herein have recognized the above issues and identified an approach for adjusting one or more parameters of the anticipatory controller of the exhaust gas sensor responsive to a type of oxygen sensor degradation. The type of oxygen sensor degradation may include a filter degradation or a delay degradation. In one example, the filter degradation may be indicated by a degraded time constant being greater than an expected time constant and the delay degradation may be indicated by a degraded time delay being greater than an expected time delay. A magnitude of the sensor degradation may be determined from the degraded time constant and/or degraded time delay. Adjusting one or more parameters of the anticipatory controller may include adjusting a proportional gain, an integral gain, a controller time constant, and a controller time delay. The controller time constant and time delay may be utilized by a delay compensator of the anticipatory controller.
In one example, the parameters of the anticipatory controller may be adjusted by a first amount responsive to a delay degradation and the parameters of the anticipatory controller may be adjusted by a second, different, amount responsive to a filter degradation. Fuel injection of the engine may then be adjusted responsive to exhaust oxygen feedback from the anticipatory controller. The amount of adjusting the parameters may be further based on the magnitude of the degraded time constant and/or degraded time delay. As such, the anticipatory controller may be adapted based on the type and magnitude of the degradation behavior. In this way, performance of the air-fuel control system may be increased.
The above advantages and other advantages, and features of the present description will be readily apparent from the following Detailed Description when taken alone or in connection with the accompanying drawings.
It should be understood that the summary above is provided to introduce in simplified form a selection of concepts that are further described in the detailed description. It is not meant to identify key or essential features of the claimed subject matter, the scope of which is defined uniquely by the claims that follow the detailed description. Furthermore, the claimed subject matter is not limited to implementations that solve any disadvantages noted above or in any part of this disclosure.